I have a customer who has designed a board using the ADV7611 and is encountering the following:
We have an unpowered ADV7611 board connected to an HDMI source. The HDMI source does not disable the TMDS lines even though Hot Plug Detect is de-asserted and the EDID PROM NAKs.
I am not sure what most PCs would do in this case.
It appears that the 3.3V on the TMDS lines is getting onto the 3.3V bus through the ADV7611 (assuming through the protection diodes)
Is there any buffering on the TMDS inputs of the chip to prevent this from happening or do we need to power the 3.3V to the chip all the time?
Any other suggestions?
Our system architecture is not typical and does not lend itself to fixing this in a straightforward fashion.
I have explained that the device is operating as specified in table 3 of the datasheet. The digital inputs cannot exceed 0.3V for an unpowered device since DVDDIO = 0V. Exceeding this causes the input protection diodes to activate. Are there other HDMI receivers that have some kind of power-off protection? Do you have any additional recommendations for this senario? Thanks,